Polyphase choking coils for rectifiers



B. B. SCHAFER.

POLYPHASE CHOKING COILS FOR'RECTIHERS.

APPLICATION man JULY 1920.

1,41 8,6859 Patented Apr. 192:

FFHCE;

BELA BEN6 scEAFER, 0F BADEN, SWITZERLAND, assrenon TO GLEICHRICHTER-.AKTIENGESELLSCHAFT, 0E GLARUS, SWITZERLAND.

POLYPHASE CHOKIN G COILS FOR RECTIFIERS.

Specification of Letters Patent. Patented Apr. 25, 1922- Applieationfiled July 14, 1920. Serial No. 396,298.

T 0 all who? it may concern;

Be it known that I, BI JLA BnNo SCHAFER,

a citizen of the German Realm, residing at No. 39 Schartenstrasse,Baden, Switzerland, have invented certain new and useful Iniprovementsin Polyphase Choking Coils-for Rectifiers, ofwhich the following is aspecification.

As is well known, the parallel connection ofa plurality of anodes of an'icrcury vapour rectifier can be safely effected by connectin chokingcoils in series therewith. In or er to counteract the rise of voltagewhich otherwise occurs with increasing loads, either a single chokingcoil may be connected in series. with each anode, or the same ironcoremay carry as many coils as there are alternating current phases. Inthe case of a six-phase rectifier, six anode coils 8 -8 (see the figure)may for instance be mounted upon an iron framing (I with three pillars;in each case it being'preterable to place the coils having the greatestdifference.

in voltage upon the same pillar. In the case.

of a parallel connection of a plurality of rectifiers, as many suchsix-phase choking coils are to be used as there are rectifier-s to beoperated at one and the same time.

It has been found that in order to effectthe parallel connection with asufficicnt de gree of safety, the voltage drop caused by the chokingcoils must be made comparatively large. The object of the presentinvention is to reduce the voltage drop on the direct current sidewithout reducing the degree of safety as regards parallel working and isattained according to the present invention b y-providing additionalcoils S, S, S, in addition to the usual anode coils s,s,, carrying thephase currents. lVe find the closed additional windingson the chokingcoil cores oppose any change in the field and therefore cause theflattenin of the curve of the continuous current, which reduces thevoltage drop on the continuous current side.

. Any irregularities which may occur during the parallel working of the!rectifiers have a much smallervfrequency and are therefore hardly dampeddown at all so that the choking coil acts favourably with regard to theparallel working and at the same time causes a reduction in the voltagedrop on the continuous current side. These additional coils may eitherbe short-circuited or be closed independently over a suitable ohmic orinduction free resistance; thus they do not carry directly the anodecurrents. The effect of the additional closed windings, viz., the safereduction of the essential voltage drop cannot be obtained by means suchasthe weakening of the main choking coils.

In the figure of the accompanyingdrawings: t is the n-phase alternatingcurrent supply, for instance for six phases ),"p,,; g is the rectifierwith the anodes a,-a and thecathode It.

The herein described arrangement of the additional choking coil may beemployed with any desired number of phases, and can also be used withadvantage in rectifiers of any type where choking coils have to beincluded in the several phase leads.

What I claim isz- Regulating ap 'iaratus for the parallel I.GOIlIlPCbIOII of a plurality of mercury vapour rectifier anodesincluding a polyphasc source of energy. a mercury rectifier with aplurality of anodes, connections between the respective phases of thesource of energy and the anodes of the IECtlfiQIQ GHCll of saidconnections including a. choking coil, -a magnetic core for said coilsand separate additional coils in inductive relation to the said chokingcoiils and circuits of said additional coils inc uding respectively anoninductive resistance.

In testimony whereof I have signed my name to this specification.

BELA BENo soHAFER.

